An animal model of cardiogenic shock has been developed in the intact anesthetized dog. Selective damage to the myocardium is produced following intravenous administration of a well characterized protein isolated from the venom of the western diamondback rattlesnake, Crotalus atrox. A dose-dependent shock-like state is produced in the dog which results in death of the animal in 15 to 60 minutes at a dose level of 2 mg pure protein/kg body weight. In the present investigation the purified protein will be administered (I.V) in lethal and sub-lethal doses to beagle dogs and the following parameters continuously monitored: heart, ECG, systemic arterial, right ventricular, left ventricular end-diastolic, pulmonary artery, central venous and left atrial (wedge) pressures. In addition, cardiac output, arterial pCO2, p02 and pH will be determined at pre- established time intervals. Following injection of the protein, blood samples will be drawn for complete blood profile analysis and immediately after death, gross necropsy performed and tissues taken for complete histopathologic, electron microscopic, cytochemical and biochemical analyses. The objective of these studies will be not only to elucidate the sequence of cellular changes induced in the myocardium by the cardiac toxin but also to pinpoint its molecular site of action. Being a well characterized protein it will be possible, for example, to tag the protein with isotopes or make antibodies against it. Ultimately, if this model proves successful, it will provide a very specific and predictable system in which to study therapeutic agents for the treatment and management of the patient with cardiogenic shock.